1. Field of the Invention
The present invention relates to a scroll compressor, and in particular to a rotation preventive device for a scroll compressor which is capable of preventing a rotation of a scroll compressor.
2. Description of the Background Art
Generally, a scroll compressor compresses a fluid such as air or refrigerant gas, etc. by orbiting in a state storing gas between two wraps having an involute shape.
As depicted in FIG. 1, the scroll compressor is constructed with a power generating part generating a driving force and a compressing mechanism part compressing gas by the driving force transmitted from the power generating part.
FIG. 1 is a longitudinal sectional view illustrating a compressing mechanism part of the conventional scroll compressor.
As depicted in FIG. 1, in the compressing mechanism part of the conventional scroll compressor, a fixed scroll 2 having an involute-shaped wrap 2a is combined with the upper surface of a frame 1, and an orbiting scroll 3 having an involute-shaped wrap 3a engaging with the wrap 2a of the fixed scroll 2 is eccentrically combined between the frame 1 and the fixed scroll 2 so as to perform an orbiting motion.
A suction hole 2b at which a fluid is sucked is formed at the side of the fixed scroll 2, and a discharge hole 2c is formed at the upper central portion of the fixed scroll 2 in order to discharge compressed gas.
A boss portion 3d projecting from the bottom surface of the orbiting scroll 3 is combined with an eccentricity portion 4a of a rotational shaft 4 rotated by a power generating part (not shown).
Particularly, a rotation preventive member 10 called as an oldham coupling is installed between the frame 1 and the orbiting scroll 3 in order to prevent a rotation of the orbiting scroll 3.
In FIG. 1, unexplained reference numeral P1 and P2 indicate a compressive space formed between the wrap 2a of the fixed scroll 2 and the wrap 3a of the orbiting scroll 3.
FIG. 2 is a disassembled perspective view illustrating a combination relation of the rotation preventive member in more detail.
In the rotation preventive member 10, a first and a second keys 12a, 12b projecting from the upper surface of a ring body 11 as a rectangular shape are placed in a straight line, and a third and a fourth keys 12c, 12d projecting from the bottom surface of the ring body 11 as a rectangular shape are placed in a straight line at right angles to the straight line connecting the first and the second keys 12a, 12b. 
In order to insert the first and the second keys 12a, 12b and move them in a straight line, key grooves 3b, 3c are respectively formed at the bottom surface of the orbiting scroll 3 in a straight line.
In order to insert the third and the fourth keys 12c, 12d and move them in a straight line, key grooves 1a, 1b are respectively formed at the upper surface of the frame 1 in a straight line.
In addition, as depicted in FIG. 1, a through hole 1c at which the rotational shaft 4 penetrates through is formed at the central portion of the frame 1, and a step portion 1d forming a thrust bearing face is formed around the through hole 1c in order to support rotatively the bottom surface of the orbiting scroll 3.
Accordingly, when the rotation preventive member 10 is placed between the frame 1 and the orbiting scroll 3, the first and the second keys 12a, 12b are respectively inserted into the key grooves 3b, 3c of the orbiting scroll 3, and the third and the fourth keys 12c, 12d are respectively inserted into the key grooves 1a, 1b of the frame 1.
The operation of the conventional scroll compressor will be described with reference to accompanying FIG. 3.
When power is applied to the power generating part (not shown), a driving force generated by the power generating part is transmitted to the rotational shaft 4, the orbiting scroll 3 orbits by engaging with the fixed scroll 2 by the rotation preventive member 10, in the orbiting process, while the pair of compressing spaces (P1) (P2) are consecutively moved to the discharge hole 2c, a body capacity of the pair of compressing spaces (P1) (P2) existed between the wrap 2a of the fixed scroll 2 and the wrap 3a of the orbiting scroll 3 is gradually decreased, accordingly gas sucked through the suction hole 2b is discharged outside through the discharge hole 2c. 
In more detail, the orbiting scroll 3 tends to rotate eccentrically together with the rotational shaft 4, however because each key 12a, 12b, 12c, 12d of the rotation preventive member 10 is inserted into each key groove 3b, 3c of the orbiting scroll 3 and 1a, 1b of the frame 1 slidable only in a radial direction, the side of each key 12a, 12b, 12c, 12d contacts to the correspondence face of each key groove 3b, 3c, 1a, 1b, accordingly it is possible to prevent the orbiting scroll 3 from rotating.
Accordingly, under the condition restricted to perform the rotating motion by the rotation preventive member 10, the orbiting scroll 3 can compress a fluid while performing the orbiting motion in a specific orbit around the upper surface of the frame 1.
However, in the conventional scroll compressor, because the rotation preventive member 10 has a ring shape, as depicted in FIG. 4, when the orbiting scroll 3 orbits, a bending stress occurs on the ring body 11 by a reaction force F0, Ff acting on each contacting face (001) (002) (0f1) (0f2) of each key (12a, 12b), (12c, 12d).
Because the bending stress occurred at the ring body 11 is relatively larger than a general tension stress or a compressive stress, the rotation preventive member 10 may be deformed. Accordingly, in order to prevent the deformation of the rotation preventive member 10, the rotation preventive member 10 has to be designed in large, accordingly the cost of materials has to be increased.
In addition, when the rotation preventive member 10 is designed in large, a weight of the rotation preventive member 10 is increased, a reaction force variation range of each key 12a, 12b, 12c, 12d greatly influenced by an inertia is increased, accordingly a maximum reaction force acting on each key 12a, 12b, 12c, 12d of the rotation preventive member 10 is increased.
In more detail, FIG. 5 is a graph illustrating a reaction force value occurred at each contacting face (001) (002) (0f1) (0f2) of the rotation preventive member 10 according to an orbit angle when a mass of the rotation preventive member 10 is one third of a mass of the orbiting scroll 3. FIG. 6 is a graph illustrating a reaction force value occurred at each contacting face (001) (002) (0f1) (0f2) of the rotation preventive member 10 according to an orbit angle when a mass of the rotation preventive member 10 is 0. With reference to FIGS. 5 and 6, a reaction force between the contacting faces (001) (002) of the rotation preventive member 10 contacting to the orbiting scroll 3 is increased as a mass of the rotation preventive member 10 is increased.
Accordingly, abrasion of each key 12a, 12b, 12c, 12d is increased in accordance with an increase of a mass of the rotation preventive member 10, according to it a leakage of compressing gas may be occurred and a noise due to collision between each key 12a, 12b, 12c, 12d with each key groove 3b, 3c, 1a, 1b may be increased.
Accordingly, in order to solve above-mentioned problems, it is an object of the present invention to provide a rotation preventive device for a scroll compressor which is capable of retrenching a production cost by reducing a size of a rotation preventive member so as to act a tension stress and a compressive stress on the rotation preventive member besides a bending stress.
It is another object of the present invention to provide a rotation preventive device for a scroll compressor which is capable of minimizing an abrasion occurrence and improving a reliability of a compressor by reducing a reaction force between each key and each key groove by materializing a lightweight rotation preventive member.
In order to achieve the above-mentioned objects, a rotation preventive device for a scroll compressor in accordance with the present invention includes a ring body formed as a ring shape and placed between an orbiting scroll and a frame, a plurality of keys respectively projecting from the ring body and inserted into each key groove of the orbiting scroll and the frame, wherein the ring body is formed so as to have a body capacity linearly connected with the keys abutting each other.
Each key has a contacting face contacted to each key groove, and the ring body is formed so as to have a body capacity linearly connected with the contacting faces abutting each other.
The ring body is formed so as to have a body capacity linearly connected with the centers of the contacting faces abutting each other.
The ring body is formed by linearly connecting the both ends of the contacting face with the both ends of the other contacting face.
The ring body is formed as a rectangular shape in accordance with an embodiment of the present invention.
The ring body is formed as an expanded shape by increasing a sectional area of at least one of a medial surface or a lateral outer surface in accordance with another embodiment of the present invention.
Herein, the medial surface of the ring body connects each key straightly, and the lateral surface of the ring body connects each key circularly.
The lateral surface of the ring body connects each key straightly, and the medial surface of the ring body connects each key circularly.
Two of the plurality of keys are respectively formed at the upper surface and the bottom surface of the ring body at regular intervals.
In a rotation preventive device for a scroll compressor in accordance with the present invention, by forming a rotation preventive member so as to act a tension stress and a compressive stress besides a bending stress, it is possible to fabricate the rotation preventive member as small and light weight, accordingly the cost of materials can be reduced. In addition, by reducing abrasion between each key and each key groove, a stability of the orbiting scroll can be maintained, and by preventing a leakage of gas from happening, a reliability and an efficiency of a compressor can be improved.